1. Technical Field of the Invention
The present invention generally relates to a differential gear assembly wherein a pinion pin is supported within a differential housing such that the differential housing can be made lighter. More specifically, the present invention relates to a differential gear assembly wherein the pinion pin is supported directly by a ring gear and positioned relative to the ring gear such that it has potential for the center of mass of the ring gear to be aligned with the center of mass of the pinion pin to substantially laterally balance the differential gear assembly, to the ring gear.
2. Description of the Prior Art
In an automotive vehicle, a differential gear assembly is used to transfer power from a rotating driveshaft to the axles and wheels of the vehicle. The rotating driveshaft of the vehicle engages a ring gear which is mounted onto a differential housing. The end of the driveshaft and the ring gear are adapted to transfer rotation from the drive shaft to the differential housing such that the differential housing rotates transverse to the driveshaft. Within the differential housing, the ends of the axles of the vehicle are supported and connected to the differential housing through a differential gear set, such as a bevel differential gear set. Thus, the ring gear of the differential housing allows the driveshaft to rotate the differential housing in a direction transverse to the driveshaft, whereby the differential gear set rotates the axles of the vehicle to drive the wheels of the vehicle.
Typically the differential gear set includes a pair of side gears which are attached directly to the axles, and a pair of pinion gears which interconnect the side gears. Most commonly, the pinion gears are supported by a pinion pin which extends across the differential housing. The pinion gears are allowed to rotate on the pinion pin thereby allowing the vehicle axles to rotate relative to one another. The rotational load is transferred from the driveshaft, to the ring gear, through the differential housing and to the pinion pin. Therefore, the differential housing must be large and thick so as to support the load being transferred therethrough. Additionally, in most conventional differential gear assemblies, the centroid (center of mass) of the ring gear is not aligned with the centroid of the pinion pin, thereby causing an unpredictable tipping moment along the axis of the axles. This tipping moment causes NVH (Noise, Vibration, Harshness), durability, and efficiency degradation.
As seen from the above, there is a need to improve the structural integrity of a differential gear assembly while also decreasing weight.
It is therefore an object of this invention to provide a differential gear assembly with a differential housing and a ring gear having features which allow the pinion pin to be attached directly to the ring gear, thereby removing the differential housing from the load path and allowing the differential housing to be designed with less structural size and weight.
Additionally, it is a further object of the present invention to provide a differential gear assembly wherein the center of mass of the ring gear is aligned with the center of mass of the pinion pin to reduce the tipping moment (lateral unbalance) along the axis of the axles.
The disadvantages of the prior art are overcome by providing a differential gear assembly, in accordance with the present invention, in which the pinion gear is attached directly to the ring gear, thereby removing the differential housing from the load path.
In one aspect of the present invention, the differential gear assembly includes a pinion pin secured to and extending diametrically across the ring gear. The ring gear includes features that receive the ends of the pinion pin and to position the pinion pin relative to the ring gear such that the center of mass of the ring gear is aligned with the center of mass of the pinion pin.
In another aspect of the present invention, the pinion pin is secured to the ring gear by the differential housing.
In still another aspect of the present invention, the pinion pin is secured to the ring gear by threaded fasteners.